This application addresses broad Challenge Area (15) Translational Science, and specific Challenge Topic 15-OD(ORDR)-101* "Pilot projects for prevention, early detection and treatment of rare diseases." Lymphangioleiomyomatosis (LAM) is an often-fatal rare disease affecting young women, characterized pathologically by a diffuse infiltration of the lungs with abnormal smooth muscle cells and cystic degeneration of the lung parenchyma. LAM occurs as an isolated disorder (sporadic LAM) as well as in women with tuberous sclerosis complex (TSC, TSC-LAM). Renal angiomyolipomas are found in ~60% of sporadic LAM patients. Angiomyolipomas are benign mesenchymal tumors consisting of abnormal thick-walled vessels, smooth muscle cells, and fat cells. The smooth muscle cells of LAM and angiomyolipomas are strikingly similar, expressing multiple melanocytic proteins, leading to the hypothesis that they are derived from a neural crest progenitor cell. The first key objective of this proposal is to separately define the gene and microRNA expression profiles of angiomyolipomas and LAM cells, to help define their cell-of-origin and possible response to hormonal therapies.The second key objective is to determine the frequency of somatic point and genomic mutations in TSC1 and TSC2 in sporadic LAM, and to determine whether activating mutations in Rheb are associated with sporadic LAM. Our third key objective is to identify other genetic events associated with LAM and angiomyolipomas. Based on analogy to other neoplastic processes, we expect to find mutations in other genes, providing insight into pathogenesis and therapy. We will use three parallel approaches. First, we will define regions of chromosomal loss or gain using a high resolution genome-wide SNP approach. Second, we will seek specific mutations in more than 400 oncogenes using Oncomap. Third, we will directly sequence all exons of 2,000 tumor-associated genes to comprehensively screen for other mutations. Thus, this proposal will address some of the most critical questions in LAM pathogenesis and biology. First, how broad is the association between TSC1 or TSC2 mutations and sporadic LAM? Second, what other mutations or genomic events that can be therapeutically targeted participate in LAM pathogenesis? Third, what does the expression profile of LAM cells reveal about the cell-of-origin, role of estrogen, and mechanisms of lung destruction in LAM? We strongly believe that answers to these questions will elucidate cellular pathways relevant to LAM, as well as other related disorders, and will also provide the opportunity for therapeutic intervention in this all-too-often progressive and fatal disorder. PUBLIC HEALTH RELEVANCE: Lymphangioleiomyomatosis (LAM) is a rare disease affecting almost exclusively women, for which lung transplantation is the only proven treatment. In this proposal we will define the expression characteristics of LAM cells, enabling dissection of its lineage, and define the genomic alterations that occur in LAM. These studies will provide insight into how this disease develops, and enable novel treatment approaches to prevent lung destruction in women with LAM.